/*
 * Copyright 2002-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package org.springframework.security.context;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.SmartApplicationListener;
import org.springframework.util.Assert;

import java.util.ArrayList;
import java.util.List;

/**
 * Used for delegating to a number of SmartApplicationListener instances. This is useful when needing to register an
 * SmartApplicationListener with the ApplicationContext programmatically.
 *
 * @author Rob Winch
 */
public final class DelegatingApplicationListener implements ApplicationListener<ApplicationEvent> {
    private List<SmartApplicationListener> listeners = new ArrayList<SmartApplicationListener>();

    public void onApplicationEvent(ApplicationEvent event) {
        if(event == null) {
            return;
        }
        for(SmartApplicationListener listener : listeners) {
            Object source = event.getSource();
            if(source != null && listener.supportsEventType(event.getClass()) && listener.supportsSourceType(source.getClass())) {
                listener.onApplicationEvent(event);
            }
        }
    }

    /**
     * Adds a new SmartApplicationListener to use.
     *
     * @param smartApplicationListener the SmartApplicationListener to use. Cannot be null.
     */
    public void addListener(SmartApplicationListener smartApplicationListener) {
        Assert.notNull(smartApplicationListener, "smartApplicationListener cannot be null");
        listeners.add(smartApplicationListener);
    }
}
